The mountain pine beetle (Dendroctonus ponderosae; MPB) is an eruptive bark beetle species afecting pine forests of western North America. MPB are exposed to volatile monoterpenes, which are important host defense chemicals. We assessed the toxicity of the ten most abundant monoterpenes of lodgepole pine (Pinus contorta), a major host in the current MPB epidemic, against adult MPB from two locations in British Columbia, Canada. Monoterpenes were tested as individual volatiles and included (−)-β-phellandrene, (+)-3-carene, myrcene, terpinolene, and both enantiomers of α-pinene, β-pinene and limonene. Dose-mortality experiments identifed (−)-limonene as the most toxic (LC50: 32μL/L), and (−)-α-pinene (LC50: 290μL/L) and terpinolene (LC50: >500μL/L) as the least toxic. MPB body weight had a signifcant positive efect on the ability to survive most monoterpene volatiles, while sex did not have a signifcant efect with most monoterpenes. This study helps to quantitatively defne the efects of individual monoterpenes towards MPB mortality, which is critical when assessing the variable monoterpene chemical defense profles of its host species.